Engine analyzer with self-synchronizing sweep



May 15, 1962 J. E. LINDBERG, JR

ENGINE ANALYZER WITH SELF-SYNCHRONIZING SWEEP Filed June 23, 1955 7 Sheets-Sheet 1 ENG/IVE INI rm TED SIGNHL OPEN FOR F.4sr SWEEP SENSITIVE GER LIGHT TRANSDU INVENTOR.

JOHN E. L/NDBER6',JR BY ATTORNEY May 15, 1962 J. E. LINDBERG, JR

ENGINE ANALYZER WITH SELF-SYNCHRONIZING SWEEP Filed June 23, 1955 7 Sheets-Sheet 2 160' 200 Angle of L/ghf Wedge INVENTOR. JOHN E. L//VOBR6,JR. BY @1 ATTORNEY May 15, 1962 J. E. LINDBERG, JR 3,034,343

ENGINE ANALYZER WITH SELF-SYNCHRONIZING SWEEP Filed June 23, 1955 7 Sheets-Sheet 3 INVENTOR. I JOHN E. LINDBERGJR.

dAM ZQM ATTORNEY May 15, 1962 J. E. LINDBERG, JR

ENGINE ANALYZER WITH SELF-SYNCHRONIZING SWEEP Filed June 23, 1955 AMPLIFIER 8 1/ msERzaumraei l/Z l meme) I 7 Sheets-Sheet 4 ENG NE,

Engine Crank Angle Degrees Ignition Pickup Thrust Picku- Pressure Picku ibration Pickup Malian Pickup Torque Pickup Temperature Picku r Propeller Dynamic Balance ve lac/1y Pickup IN VEN TOR.

Arron/WY y 1962 J. E. LINDBERG, JR 3,034,343

ENGINE ANALYZER WITH SELF-SYNCHRONIZING SWEEP Filed June 23, 1955 '7 Sheets-Sheet 5 7 22 L TI" Engine lnifiafed Signal I44 y/ Q Q a fi E E M3 E 32 0 90 I80" 270- 3&0

WEDGE ANGLE 32%??? /45 fig. 2 5.

%A 52 I [45 4.5 2 will III ll" lmlllllll lfllllllhl INVENTOR.

JOHN E- LINDBERQJR,

BYQIQMAMA'M A TTOR/VEY May 15, 1962 J. E. LINDBERG, JR

ENGINE ANALYZER WITH SELF-SYNCHRONIZING SWEEP Filed June 23, 1955 7 Sheets-Sheet 6 70 AMPLIFIER mm. E ENG/NE VOL 746E RIGULNTUR SWITCH SELECTOR & CHI/047E154? WEE (RESOLVER) (253 SWITCH ENGINE A .3 PHA E GENERRTDZ ENGINE B 3 PHASE qsNEEn 7m ENG/NE 0 1 3 PHAS Gil-N52470:?

IN V EN TOR.

ATTO

JOHN E. L/NDBERGJR.

R/VEY May 15, 1962 J. E. LINDBERG, JR

ENGINE ANALYZER WITH SELF-SYNCHRONIZING SWEEP '7 Sheets-Sheet 7 Filed June 25, 1955 LIGHT TRQNSDLCE I NVENTOR.

JOHN E. Ll/VDBE/PQJR. BY aw 5am AT TOR/V5) i United make adjustments in the engine.

3,034,343 ENGINE ANALYZER WITH SELF-SYNCHRGNIZ- ING SWEEP John E. Lindherg, Jr., 3296 Springhill Road, Lafayette, Calif. Filed June 23, 1955, Ser. No. 517,577 18 -Claims. (Cl. 73-115) This invention relates to an improved engine analyzer and more particularly relates to a positively synchronized sweep circuit for an engine analyzer.

Engine analyzers, such as the one illustrated in my earlier Patent 2,518,427, are used to investigate the performance of engines while they are in actual operation. Certain signals from any of various parts of the engine are impressed across one set of deflection plates in a cathode ray oscilloscope, and a sweep circuit is impressed across the other set of deflection plates. The result is a pattern that, when studied, indicates the performance of the engine.

Synchronization of the sweep circuit with the engine signal circuit has been a very difiicult problem. Heretofore, sweep circuits have been initiated independently of the engine by charging and discharging a condenser or by some other means that varies the voltage at a uniform rate over a predetermined period of time, so as to change the voltage difierential between the cathode ray plates uniformly with time. But this type of sweep circuit was unable to cope with the synchronization problem, because an engine necessarily operates at diiferent speeds, which vary tremendously. Whenever the engine speed changed, the sweep circuit tended to lengthen or shorten the diagram, and measurement of absolute lengths along the diagram became meaningless, since the lengths could not be related directly to engine conditions.

The prior art sought to solve this problem by providing, in various ways, compensation from an engine-initiated pulse. A typical compensator is shown in the E. F. Weller, in, et al., Patent No. 2,645,715. There, the charging rate of the sweep-generating condenser is regulated by a circuit which is controlled by pulses from the engine, to

provide a constant amplitude sweep circuit. In other words, the independent sweep circuit was modified in the attempt to synchronize the voltage change with the engine speed. The modifying circuit for this compensating apparatus was very complex; the one referred to in E. F. Weller, in, et al., Patent 2,645,715 utilized six electronic tubes plus a mechanical circuit breaker. The best circuit currently in use is even more complex, and includes eleven electronic tubes. This reliance on compensators has left synchronization a diflicult and expensive problem; special items of equipment, such as special generators, have been required; and the results have still not been completely satisfactory, especially during periods of acceleration and deceleration of the engine being studied.

I have solved these problems by a new approach to the sweep circuit. My invention obtains its sweep circuit synchronization directly from the engine being analyzed. My new sweep is always necessarily in phase with the engine signal, and synchronization of the sweep with the engine cycle is completely unaffected by changes in speed.

In addition to achieving the object of perfect synchronization, my sweep circuit has other remarkable features; it uses a standard generator which may already be on the engine, and contains no other moving parts.

It makes it possible to time the initiation of the sweep,

directly in the cabin of the plane instead of having to In addition, as will appear, the engine provides a sweep circuit of great versatility; the type of sweep can be varied for diiferent kinds of analysis simply by throwing a switch which changes circuit impedance.

ice

In brief, my invention contemplates obtaining the basic sweep signal from a generator driven by the engine and running at engine cycle speed. In a typical example, two currents ninety degrees out of phase are obtained from the single generator, and these are impressed upon the two pairs of deflection plates of an auxiliary cathode ray tube so as to give a circular sweep. This signalan electron beam moving in a circleis used as a light source, and the light is passed through an optical wedge to a light-sensitive transducer. The resulting electric signal, properly amplified if necessary can then be impressed across the sweep plates of the cathode ray tube of the engine analyzer itself. Basically, then, the invention operates byfirst using an engine to generate a circular sweep of light whose cycle therefore depends directly on the engine cycle; this circular-moving light beam is then used in combination with an optical wedge and a phototransducer to produce a varying electric voltage suitable for control of the engine analyzer sweep circuit.

Other features, objects, and advantages of the invention will become apparent from the followingdescription presented in accordance with 35 U.S.C. 112.

In the drawings:

FIG. 1 is a diagrammatic representation of an apparatus and simple circuit embodying the principles of my invention.

FIG. 2 is a view in front elevation of one form of optical wedge suitable for use in my invention, wherein the light transmission varies uniformly with angular position around a full 360 cycle.

FIG. 3 is a view similar to FIG. 2 of another type of optical wedge also useful with my invention, wherein the light transmission varies uniformly with angular position over a small angle and remains unchanged over the remainder of the cycle.

FIG. 4 is a view similar to FIG. 2 showing another type of optical wedge I employ, wherein a square wave can be generated by having two arcs of different transmission, each are maintaining its own transmission at a uniform level. a

optical wedge wherein there is a series of arcuate segments made up of two types, which alternate. In one type each segment extends the same arcuate distance and varies uniformly in transmission with its angular position. Each of the other arcuate segments extends an identical arcuate distance and maintains a uniform light intensity at the level of the end of the preceding variable segment.

FIG. 6 is a view similar to FIG. 2 of another type of optical wedge, wherein there are two segments, one of which is relatively short and varies uniformly over its are between zero transmission and fifty percent transmission, While the other, much longer, segment varies uniformly over its are from fifty percent transmission and one-hundred percent transmission.

FIG. 7 is a diagram, plotting angle of light wedge against percent of light transmission, for each of the wedges shown in FIGS. 2 to 6, and corresponding to the final sweep curve for each wedge.

FIG. 8 is an illustration of one type of engine analyzer pattern, obtained from a signal initiated by the engine and from the sweep given by the wedge of FIG. 2.

FIG. 9 is an illustration of a pattern obtained from the same engine signal as that of FIG. 8 but using the sweep given by the wedge of FIG. 3.

FIG. 10 is an illustration of a pattern obtained from A.

the same engine signal as FIGS. 8 and 9, using the wedge of FIG. 6 to obtain the sweep.

FIG. 11 is an illustration of another type of pattern, obtained from a different engine signal, using the sweep given by the wedge of FIG. 2.

FIG. 12 is an illustration of a pattern obtained from the same signal as that of FIG. 11 but using the sweep given by the'wed ge of FIG. 5.

FIG. 13 is a view similar to FIGS. 2 to 7, showing a four-band combination wedge, having annular bands at different radii to correspond to the wedges siown'in FIGS. 2, 3,4, and 6.

FIG. 14' is a view similar to FIG. 2 showing a wedge that is indexed as to angular position.

2 FIG. 15 is a view similar to FIG. 14 showing a disc that is'adapted' to overlie any of various wedges and index its angular positions. I

FIG. 16 is a diagrammatic view showing a more complex apparatus and circuit than FIG. 1, but also embodying the principles of my invention. 7

FIG, 17 is a view showing a modified form of circuit for obtaining the circular sweep directly from a threephase generator. 1

FIG. 18 is a view showing another modified form of circuiL-io'r obtaining the circular sweep indirectly from a three-phase generator, I 7

1316119 is a view showing another modified form of circuit, for obtaining the circular 'sweep directly from a single-phase generator. 1

- FIG. 20 is aview showing another modified form of circuit for obtaining a circular sweep from a three-phase generator.

,FIG. 21 is a view showing another modified apparatus and; circuit omitting the lens.

FIG. 22 is a diagram similar to FIG. 7, on a reduced scale, showing the curve produced by a calibrated wedge of'FlG. l4.

FIG--23 is an illustration of a pattern like that of FIG. 1, but using the calibrated wedge of FIG. 14.

1. SIMPLE ANALYZER USING THE PRESENT "INVENTION (FIGS.,1 AND,21)

While some of the applications of my invention involve complex circuits and apparatus, many of the basic pfinciples are illustrated in the simple analyzers shown in FIGS. 1 and 21, and the more complex applications will be better understood after considering this simple and practical embodiment.

(a) A Simple Circular Sweep 4 (b) The Optical Wedge The next step is the transmission of the light signal 36 from the cathode-ray tube 39 through an optical wedge 49, preferably in contact with the cathode-ray tube, but

' shown apart therefrom for illustrative purposes only. The

wedge 40 shown in FIG. 1 is a sheet 4-1 of film, glass or other transparent material on which is impressed (as by photographic or other printing or by a controlled metallic deposit in vacuum or by any other suitable means) a pattern 42, in which the light transmission increases at a constant rate from zero (or very low) transmission at 43 (0) to full (or very high) transmission at '44, which is ljust short of 360. In other words, the electron beam 35 used, some of which will subsequently be described. But

the wedge '40 will produce a rotating beam 45 Whose intensity varies uniformly with its angular position as it moves around a circle, the light intensity increasing at a A uniform rate from nothing to its full amount and then There are many ways of obtaining a circular sweep} several of which are shown in the drawings, but two of.

the simplest are shown in FIGS. 1 and 21. In each, an engine 20 to be analyzed drives a rotatable magnet 21 in a two-phase generator 22 at engine cycle speed, which,

in an airplane engine, is one-half the crankshaft speed. The two-phase generator 22 has two stationary coils 23 and 24 located ninety degrees outof phase. Lead Wires 25 and 26 extend from the coil 23 to a cathode-ray tube '30 and place a varying (sine wave) potential across the fhorizontal deflection plates 31, 32. Similarly, lead wires that'do not afiect synchronization of the angle of the closed sweep with the enginecycle can, .or many poses, be disregarded. a

sharply falling to nothing as the next cycle begins. Moreover, the cycle is obviously in perfect phase with the engine 20.

(c) The Lens 48 (FIG. 1 Only) The next step in the FIG. 1 device is to focus the rotating beam 45 of changing intensity on a single motionless spot 47, so that instead of appearing as a beam 36 moving in a circular path, it will appear as a single stationary beam with varying intensity. This is .accom plished by a lens 48 placed at the proper distance from the wedge 40 and focused on the spot 47.

This step is omitted in the FIG. 21 device.

j (d) The Light-Sensitive Transducer 50 V in the wedge.) This voltage may be amplified by any suitable means such as an amplifier 52, to-obtain a voltage of the desired amplitude in the lead 53'.

While the lens 48 is useful and convenient, it is not necessary, as shown in FIG. 21. Here all the elements are the same as inFIG. 1, and are given the same numbers, except for the photo-sensitive cell 50a, which is, in this instance, a large one relative to the cathode ray tube 30, uniformly sensitive at all points on its surface. Operation is therefore identical to that described in connection with FIG. 1. The-intensity of the light beam =37 is varied in exactly the same way by the wedge 40, to give the beam 4-5 of varying intensity, and the resultant sweep circuit isidentioal to the one shown in FIG. 1. Since the tube 34} oan be a one-inch tube, there are photo-sensitive tubes 50a on the market capable ofreacting properly itnd uniformly to the beam from such atube without a ens. e rpensively than making :a large'tube 50a.

The photo-transducer '30 or 50a must be of a type that has ah'ighresponse rate. This is mentioned because some photo-transducers are slow to respond; they lag behind energy changes and do not recover quickly at the point With large tubes 30, the lens 48 can beused less I where a new cycle begins. The response rate must necessarily be high enough to reflect within small tolerances the change in light intensity which the wedge 40 produces in the light beam. Preferably it should respond in a few microseconds, and this can be obtained from available vacuum phototubes, gas phototubes, and photomultipliers. Photomultipliers have the advantage that they make it possible to eliminate any additional amplifier 52, if that is desirable, and can be connected directly to the analyzer tube 55.

Since the device is an optical system from the auxiliary cathode ray tube 30 to the photo-transducer 50, the system is best protected from stray light by enclosing it in a shield 54, which may have light-reflecting walls beyond the wedge 40.

The amplifier 52, if needed and used, is preferably of the push-pull type and can be provided with a variable control for determining the length of the ultimate sweep, so that the complete engine cycle can take up the full width of the tube 55, or only a part of the engine cycle (e.g. the ignition of one cylinder) can take up the full width of the tube.

(e) The Engine Analyzer Cathode Ray Tube 55 The varying signal from the photo-transducer 5t} having been amplified is now ready to be impressed across the sweep plates of the engine analyzer cathode ray tube 55. As shown, this may be accomplished by grounding one of the plates 56, while the lead wire 53 from the amplifier 52 is connected to the opposite plate 57. This means that the electron beam 5-8 in the tube 55 will move across the tube 55 from the plate 57 to the plate 56 (or the reverse) during each engine cycle and will, at the end oat each cycle, snap back to the plate 57 and begin moving again during a new cycle. The rate of speed of the beam 58 is constant if the engine speed is constant; if the engine speed changes, the speed of movement of the beam 58 changes. Therefore, the position of the beam 58 relative to the engine cycle is constant, with any given wedge. If the engine slows down, the beam slows down, until the engine stops and the generator 22 ceases to produce the sweep. If the engine 20 runs faster, the beam moves faster, too. In other words, when using the wedge 40, the sweep plates are impressed with a sawtooth sweep voltage in exact synchronization with the engine-driven two phase generator 22 and its circular sweep at the tube 3%).

Across the other plates 60 and 61 of the tube 55 are impressed the signal from the engine itself, which may be of the type shown in Patent 2,518,427 or may be of another type. The signal may be from an engine magneto (for studying ignition) or may be from a vibration pickup (as shown in FIG. 1), or any other engine-generated signal may be used.

(1) Operation of the FIG. 1 Apparatus When the engine 20 is running, the two-phase generator 22 generates a circular sweep 3 6 at the tube 30, necessarily perfectly synchronized with the engine cycle. The light caused by the circular beam 36 impinging on the fluorescent screen 37 passes through the optical wedge 40 and is focused by the lens 48 on the photo-transducer circuit.

This voltage, properly amplified, if necessary, is impressed across the sweep plates "56 and 57 of the analyzer cathode ray tube 55 resulting in a sweep circuit there. Meanwhile, the signal plates 60, 61 are impressed with a signal from the portion of the engine being analyzed, as provided in my Patent No. 2,518,427 or in other engine analyzer circuits, giving a result-ant pattern on the scope 55. The operation of the FIG. 21 device is identical, except for the omission of the lens 48.

(2) DIFFERENT TYPES OF WEDGES AND THEIR CORRESPONDING TYPES OF SWEEPS (FIGS. 2 TO 13) As implied earlier, different types of optical wedges 6 can be used to obtain difierent types of sweep circuits. To illustrate this principle, several different types of wedges have been illustnated, together with some of their effects on the sweep and on the analyzer patterns.

(a) Full 360 Uniformly Graduated Wedge 40 (FIGS. 2, 8, and 11) The wedge 40, as stated earlier, has its pattern 42 change uniformly with angle over a full circle from zero (or low, e.g., 10%) transmission to full (or high, e.g. 90%) transmission. This gives a saw-tooth wave of the linear type, as shown in FIG. 7 by the curve 46.

The wedge 40 may be turned around, in order to move the sweep from right to left instead of left to right, since the light will then start bright and gradually decrease at a uniform rate.

The 360 extent of the wedge 40 corresponds to the full 720 of rotation of the engine crankshaft cycle, each 2 thereof corresponding to 1 of light wedge. Thus, in an ignition diagram 65, such as that shown in FIG. 8, patterns for every cylinder appear. The same thing happens in the radio-frequency pattern 66 shown in FIG. 11, where there are gaps 67 between each cylinders diagram 68.

(b) Short-Arc Uniformly Graduated Wedge 70 (FIGS. 3 and 9) The wedge 70 shown in FIG. 3 is adapted to enlarge a portion only of the complete engine cycle and to exclude the rest of the cycle. This makes it possible to enlarge the diagram for each cylinder one cylinder at a time and study it more thoroughly. Thus, in an 18-cylinder engine, a segment 71 extending 20 of arc will cover one-eighteenth of the complete engine cycle and, by having the wedge 76 rotatable, can be used to show the complete pattern of one cylinder and to take up the whole screen 63 with this one cylinder (see FIG. 9).

The segment 71 is graduated uniformly with angle, from zero transmission at 0 to full transmission at 20. The large 340 segment that remains is blank and gives full transmission. The resultant curve 73 on the FIG. 7 diagram shows a steep linear slope extending for 20 and then perfectly flat for the remaining 340.

A typical ignition pattern 74 obtained from one cylinder by using the wedge 70 is shown in FIG. 9, Where it will be seen to be agreatly enlarged (spread-out) version of one-eighteenth of the FIG. 8 pattern.

(0) T wo-Level Wedge 75 for Square Waves (FIG. 4)

When a square wave sweep is desired, a wedge .75 like that shown in FIG. 4 may be used. One segment 76 (shown here as 15) is completely opaque and another segment 77 (shown here as 345) is fully transparent.

'Alternately the two segments 76 and 77 may be any two levels of transmission; just so that each is constant in itself. Also, the proportions shown are exemplary only, and can be varied to suit conditions. This results in the voltage curve 78' shown in FIG. 7.

(d) Gap-Eliminating Wedge 80 (FIGS. 5 and 12 The wedge 84? shown in FIG-5 is of a novel type, designed for use with radio-frequency analyzer ignition cir- 'cuits to, solve the problem indicated in FIG. 11, where there are gaps 67 in the pat-tern between each cylinder. If there normally were no gaps like this, then the presence of a gap for a whole cylinder would more clearly indicate are eighteen segments 81, whose length corresponds to the gaps 67 in the curve of FIG. 11. The eighteen segments 81 are of eighteen different transmissionsstepped their density vary uniformly-from the level of the segment 81 on one side to the level of thesegment 81 on the other Sldfi'. i i

As' a result, during each cycle,[the voltage level will vary uniformly'during the scanning of each segment '82 and will be unchanged during the scanning of each seg ment 81. The curve 83, shownin FIG. 7, results, with sloped portions 84-, corresponding to the segments 82 where the voltage increases, and level portions 85, corresponding to the segments 81. This means that the sweep at the cathode ray tube 55 will move in jerks, eliminating the level portions 81 to zero length. Because of this, the signal that produces the R.-F. diagram 66 of FIG. 11 when using the wedge 40 will produce the R.-F. diagram 86in FIG. 12 when the wedge 80 is used. The gaps 67 that show on the diagram 66 between the energized por tions 68, are'eliminated, and the curve will appear as continuous, under normal conditions. Trouble is therefore easily spotted, as is shown in FIG. 12, when the missing portion 87 means that one cylinder gave no R.-F.

signal, being shorted out. This shows much clearer and acetate in a different way. This principle is illustrated by awedge 100 shown in FIG. 13. Here four bands 101, 102, 103, and 104 are shown, though there could as well be two, three, five, or any other number of bands.

I The outer annular band 101 is graduated exactly like the wedge in FIG. 2, that is, uniformly from zero transmission to 100% transmission over the full 360 circle. The next inner band 102 is graduated exactly like the wedge 70 shown in FIG. 3, that is, from zero transmission to full transmission in a 20 arc 105 with the remaining 340 are 106 at full transmission. The next inner band 103 is graduated like the wedge 75 shown in FIG. 4, that is, a 15 segment 107 at zero transmission and a 345 segment 108 at 100% transmission. The innermost band 104 is graduated like the wedge 90 in FIG. 6, that is, from zero transmission to transmission in a 20 segment 109 and uniformly from 50% to 100% transmission in the remaining 340 segment 110.

The composite wedge 100 is used by providing a volt- 3 age regulator and a selector switch that will act to vary in some manner the voltage impressed across the deflector plates of the circle-sweep-cathode-ray tube. One such arrangement is shown in FIG. 16 (to be explained later on in more detail) where an amplified engine-generated current is sent through a selector switch 112 compirsing variable step-resistor having four positions each one of ismore easily. detected than the missing portion 6? in V the diagram 66. a

whileexamining each individual cylinder in detail, one

at a time, going from cylinder 'to cylinder.

In the wedge 90, a segment 91' (which in an 18 cylinder engine will extend 20 on the light wedge) is graduated uniformly between zero transmission and 50% transmission. The remaining segment 92 (which in this example will'occupy 340) varies uniformly from 50% transmission to 100% transmission. (The variations in transmission could vary, as a 20 arc from 12% to 52% transmission and a 340 are from 52% to 92% transmission.)

' As a result, the curve 93 shown in FIG. 7 is obtained,

having a steeply sloped portion 94 extending the first 20 and a more flatly sloped portion 95 extending the re maining 340.

In order to illustrate one type of diagram that may result from the wedge 90, FIG; 10 is included. Here a diagram 96 clearly shows one cylinder occupying one-half 7 of the screen '63, while the remaining 17 cylinders occupy the remaining hmf 98 of the screen 63.

. '30 (e) Half-and-Half Slow-Fast Wedge 90 (FIGS. 6 and 10) which determines a given radius of the circular sweep 136 and thereby sends the light formed on the screen 137 to anyone of four predetermined radii corresponding to the four bands of the wedge 100. The circuit arrangement will be explained in more detail later on. Other means for vai'ying 'the voltage could be used, and example illustrateshow a single disc may incorporate several different sweep circuit arrangements.

(g) Multi-Wedge one 300 (FIGS. 24, 25, 617101 26) is itself rotatable to place one at a time only of the wedges in its proper position between the cathode-ray tube and the light-sensitive transducer 50. The wedges are synchronized with each other to give the same zero point, by proper relativelocation on the disc 300. By way of example, four types of wedges. 301, 302, 303, and 304 are shown mounted in the disc 300, but there maybe more It should be noted-that the diagrams shown in FIGS."

8, 9, and 10 are all obtained from the same basic engine signal. Thus, the FIG. 8 diagram 65-,shows'all 18 cylindam, and each one occupies the same length; the FIG. 9

' and the remaining half by the other 17 cylinders Note that FIGS. 8 and 10 show one of the engine spark plugs or fewer wedges. No shielding problem is created by this construction, since known types of baffles can be in contact with the disc 300. This disc 300 has the advantage that there is no need to prepare a special disc 100, nor is there any need for varying or even controlling the 1 diameter of the circular sweep, thereby saving circuit elements, because each wedge is made uniform in density along each radial line. Each'd-isc 301, .302, 303, and

. 304'may be rotatable, as by sun and planetary gears 325,

and 326, forthe purpose described in the next section.

Other features of the invention shown in FIGS. 24 and 25 and not related to this multi-wedge feature, are discussed later on.

with an open secondary circuitat 99. If further investigation of this particular cylinder is'desired, it can 'be obtained by shifting the initiation of the sweep in FIG. 10, V

to. bring. the signal for that cylinder into the position where it occupies the left half of the diagram. Or the wedge used for the FIG. 9 pattern may be used.

(1'') ComposiiFoui-Band Optical Wedge'JOO (FIG. 13)

. fltiis possible to' obtain the results of several or indeed all of the wedges shown on a single disc by providing (h'lRotating the Wedge to Select the Cycle Initiation Point By making any wedgerotatable, the cycle may be initiated at anydesired pointJ Thus the wedge 70 may be used to study any cylinderignition diagram simply by rotating the wedge 70'until the proper cylinder ignition diagram is in a position occupying the 20 of are. Moreover, the initiation of the sweep forthat cylinder can be selected to initiate at any point of the cylinder cycle. Similarly, by rotation of the light wedge 40 relative to a supporting rotatable knurled ring 111 (see FIG. 16), the

made to fall at any desired point and may be used to time the analyzer to the engine cycle. This provides a very simple manner of adjusting the synchronization between the sweep and any engine-initiated signal to secure any desired point of initiation of the oscillogram on the scope 55 or 155. Moreover, cycle initiation is controlled inside the aircraft cabin rather than having to adjust the synchronization at the engine itself.

One way of providing a rotatable wedge is shown in FIG. 16, where a four-band wedge 100 is held by a friction strip 181 in a cycle-indicating ring 182, which is rotatably mounted in a fixed clinder index ring 183. A flange 184 on the ring 182 may comprise the forward portion of the light shield 154, so that the calibrations are outside the shield. The shield 184 and ring 182 are rotatable relative to the fixed cylinder index ring 103, and the wedge 100 is rotatable with or separately from. the ring 182. A lever 185 is operable from outside the shield 154 to engage the wedge 100 and lock it against rotation relative to the ring 132. This lever 185 may be mounted on a fixed rear portion 1541) of the shield 154-, and may be disengaged when adjusting the wedge 100 so that the wedge 100 will rotate with the ring 182.; then the lever 185 may be engaged to lock the wedge 100, while the ring 182 is rotated to get the proper adjustment between the ring 182 and the wedge 100.

In order to take full advantage of this cycle initiation device, one known cylinder should be differentiated, as by disconnecting its ignition leads to give an open circuit diagram. :Or the engine can be wired to give an indexing pulse at a known point in the engine cycle. At any rate, once that cylinder or cycle position is identified, all cylinders and engine events are identified by the known firing order and other constants of the engine cycle of the engine.

Starting with a known cylinder, the light wedge 100 may be rotated, by disengaging the brake lever 185' and rotating the ring 182-fiange 184 combination, until the ignition diagram of the identified cylinder is correctly located relative to the index of the indicator tube 155. If it is the No. 1 cylinder, then the ignition diagram for the No. 1 cylinder is located at the beginning of the horizontal sweep trace on the indicator cathode-ray tube 155, at zero on the index. Then the light wedge 100 is locked at this point by the lever 185.

Next, the ring 182; is rotated until the arrow labeled IGN points at the numeral 1 on the ring 183. The analyzer is now timed to the engine, and all the timing has been done in the cabin at the analyzer, instead of,

having to rotate the engine generator, as was necessary in the past. The brake lever 185 isnow disengaged.

Once this initial synchronization is done, the sweep of the indicator tube can be initiated at any selected point in the cylinder cycle (as shown on the ring 182) for any selected cylinder (as shown on ring 183) by placing the selected cycle point on the ring 132 opposite the numeral indicating the selected cylinder on'the ring 183. For example, if the IGN pointer is turned so that it points to the numeral 2 on the ring 188, the horizontal trace on the tube 155 will start at the beginning of the ignition cycle of the No. 2 cylinder. Any selected condition may similarly be displayed on the oscilloscope 155.

The discs 301, 302, 303, and 304 in the multi-wedge disc 300 may be rotated similarly, as shown in FIG. 26'.

(2') Alternative Selection Cycle Initiation Point by Rotation of the Tube Using the Structure of FIG. 24

rotation of, the cathode-ray tube 305 is more convenient.

The deflection plates and other tube circuit connections are connected to their lead wires by means of appropriate independent slip rings 306, so that rotation of'the tube 305 becomes possible. This is indicated diagrammatically, and satisfactory operation can be obtained by other means, as by flexible leads. When the tube 305 is rotatably mounted, the cycle switch 307 may be mounted concentrically with the main oscilloscope 308 and may have a toothed edge 310 that drives a gear 311. The gear 311 may be mounted on a shaft 312, and gear 313 also supported by the shaft 312 may drive a gear 314 mounted on the tube 305. The basic operation is still the same. as that described in the preceding section.

(j) Alternative Selection of Cycle Initiation Point Using A Magnetic Deflection Circuit (FIG. 25)

As is well known, the electron beam in a cathode-ray tube may be deflected either electrically or magnetically. A circuit in which a circle-sweep cathode-ray beam is controlled by magnetic deflection is shown in FIG. 25. The cycle switch 307 and associated parts are like those of the FIG. 24 device, but the gear 313 drives a gear 315 which rotates a magnetic deflection yoke 316, while the cathode-ray tube 317 stays stationary. Slip rings 318 on the yoke 316 connect with leads 320, 321, and 322 leading to a three-phase generator 323. Again operation is like that described in section h above.

(k) Indexing the Sweep Curve (FIGS. 14 and 15) The invention also makes it possible to provide indexing means in connection with any of the wedges so as to calibrate the pattern at the scope 55. This can be done by providing the wedge itself with radial lines of substantially different density from their portion of the wedge, e.g., of full transmission or .of zero transmission at spaced intervals. For example, FIG. 14 shows a wedge 140 like the wedge 40 but with four openings or blank areas 141 spaced around it at regular intervals. When the light beam 36 strikes one of these areas 141, it transmits its full intensity to the photo-transducer 50, correspondingly aflecting the sweep, as shown in curve 143 with its peaks 144 in FIG. 22, and showing as gaps 145 in FIG. 23. These lines 144 produce either full voltage or zero voltage at a particular. location on the picture tube 55, corresponding to the degrees of are where the lines are formed in the wedge, and therefore to corresponding degree in the engine cycle. Where the wedge is primarily like that of FIG. .2, the degree-indicating lines are preferably completely blank, as shown in FIG. 14, giving full transmission and thereby full voltage.

For use with curves like those of FIGS. 3 and 4, it may be more useful to have dark lines. These dark lines may be provided on the wedge itself, or they may be provided on a separate indexing disc 146 (FIG. 15) which carries nothing but a series of dark lines 147 and is adapted first to be synchronized with itswedge and then to be moved together with it when selecting the initiation points.

3 A MORECOMP'LEX ANALYZER CIRCUIT Pro. 16)

-To give some further indication of the versatility of this invention, I shall now describe a more complex circuit that takes advantage of some of the special features flowing from generation of the sweep circuit of the engine analyzer tube by means optically-responsive to a circular sweep on an auxiliary cathode-ray tube. Several features of this circuit are substantially identical with that of a simple circuit, while other features have been shown in modified form to illustrate alternate methods of accomplishing the same end results. In other instances the refinements described are completely absent from the simple circuit shown in FIG. 1.

The circuit and apparatus shown in FIG. 16 are adapted "for use with multi-engine aircraft and are therefore shown in connection with our engines herein called engines A, B, C, and D respectively. In each instance, the engine A, B, C, or D rotates a magnet 1210f a threephase generator 122a, 122b, 1220, and 122d at engine cycle speed: i.e., at one-half-the crankshaft speed in a and 125 of the generator 12-2 current-is transmitted to a resolver 165a, 165b, 1650, or 165d, which provides two sine waves 90 out of phase and adjustable relative to the engine generator 121, to time the engine to the generator. The resolver is,,in efiect a continuous resistor with four brushes 166, 1:67, 168, and 169 mounted 90 apart and linked together mechanically as a unit. All four resolvers may be on a common resistor, or they may be separate resistors. Electricalinsulation is provided so that the brushes 166 and 167, which are diametrically opposite each othensupply the current pickup which eventually will be impressed on the'horizontal plates 131 and 132 of the cathode-ray tube 130, while the brushes 168 and 169, also diametrically opposite each other, pick up the current which will ultimately beused on the vertical defiection plates 133 and 134.

An engine selector switch 170 is provided into which are connected each of the four'leads 171a, 172a, 173a, and 174a; 1711), and 172b, 1731), and 174b; 171e, 172e, 173a, and 174s; 171d, 1720!, 173d, and 174d,'from each of the four resolvers 165a, 165b, 165a, and 165d, one for each of the engines A, B, C, and D. The selector switch 170 provides a means for placing the four leads of any one engine intocontact with corresponding output leads 175, 176,177, and name leads from other three engines going at that time to a. dead end or'broken circuit.

Thcfour leads .175, .176, 177,, and 178 pass through suit-.

able amplifyingand automatic voltage-regulating means 179 toa sweep selector switch 112 which. has somewhat beendescribed above. It comprises ,four step resistor elements 113, 114, 115, and116 (one for each of the four leads 175, 176, .177, and 178) all linked together for step movement so that all the resistor elements 113, 114,

115, and 116' of the .switch' are either at step 1, or step 2,

or step-3, or step 4. This changes the'voltage levels in the lead lines 175,176,177, and 178" and therefore changes the voltageimpressedupon the deflection plates 131, 132, 133, and 134 of the cathode-ray tube i'130, which in turn change the amount of deflection of the cathode-ray 135 to produce any of four desired radii.

FIG. 27 illustrates in diagrammatic form a modifica tion of a portion of the FIG. 16 circuit, showing the fact that an engine selector switch 250 may be interposed between the engine generators 122a, 122b, 1220, and 122d and a cycle switch 260,:instead'of using thFIGQ 26 arrangement. a

Except for the refinements heretofore described,;the cathode-ray tube operates substantially thesame as the'tube 39, giving a circular sweep 136 on its fluorescent screen 137, the difierencebeing that the circular sweep 1 36 may be adjusted to any one of four'radii.

The light produced on the fluorescent screen 137 by the cathode ray is transmitted through the optical wedge 100 and focused by a lens 148 on "a photo-transposed, with its three brushes 296, 207, and 208 mounted ducer 150'. (The lens 148 may, of course, be omitted by selecting the proper photo-transducer.) The only difference in this part of the dew'ce is that the;wedge 100 j is :of the four-band type heretofore described, so that the sweep selector switch 112 makes it possible'to send'the;

light beam through any oneof the fourbands' 101, 102, 163, or 104 of thewedge 100. a I

The photo-transducer element 150 shown is of the type having a voltage impressed acrossit from a source 151 and in which the resistance to that voltage is varied by the light falling on the elementv 150; It may be a-photo a ...signal which may or may not-need amplification by amplifier 152' before it is impr'essed'as the sweep across thehorizontal deflection plates 156 and 157 of a cathj ode ray oscilloscope 155. A light shield'1'54 isagain'pro-j vided around the assembly made up of the tube-130,

wedge ltlihlens 148, and transducer 150.

- 'I'heinitiation'ofthe cycle'for' each engine A, B, (CZ-and v a 15?. D may be controlled by its resolvera, 165b, 1650,, and 165d which may be synchronized to the engine once and for all, and left there, or maybe made adjustable at any time, by rotating the four brushes in tandem. Once each engine has had its cycle synchronized to that of the other engines by adjustment of the resolvers 165, cycle initiation for all engines may be changed'by rotating the optical Wedge 10%), as described earlier.

Many types of engine signals may be analyzed, and for purposes of illustration, a typical condition switch 189 is shown diagrammatically with 36 conditions possible, including eight for each engine (or .32 altogether), three for coupling engine A to each of the other three engines, for synchronization check, and one special switch. Typicalfuses or the analyzer are illustrated by the labels on the lines leading from engine D (using circuit connection as described in my Patent 2,518,427.), showing that there is a magneto pickup for ignition analysis, a temperature pickup, a pressure pickup, a vibration pickup, a motion pickup, a torque pickup,-a propeller dynamic balance pickup, and a velocity pickup. Any one of these pickups may be selected at the condition switch for any of the engines A, B, C, and D, and studied, by Whicheverof the four sweeps is most appropriate.

. 4. OTHER MEANS FOR OBTAINING A CIRCULAR SVJEEP (FIGS. l7-2 0) (a) Obtaining a Circular Sweep Directly From a Three-1 Phase Generator. (FIG. 17)

FIG. 17 shows how a three-phase generator 200 may be connected to three pairs of deflector plates 20*1, 201a, 2&2, 2 92a, 203, 20312, arranged 120 apart in a cathoderay tube 264, to produce a circular sweep. One of each pair of plates, 291, 2%, and 203 are connected to the three phase generator 200, While the' other plate 201a, 202a, and 203a of each pair may be connected to a common lead. Since the three plates are 120 apart and since the phase variation is exactly as generated, the electron beam will move in a circular path.

(b) Obtaining the Circular Sweep Indirectly From a T hree-Phase Generator. (FIG. 18)

FlG. 18 shows another way of obtaining a circular sweeptrom thethree-phase generatorltlll, again using the tube 204 with three pairs deflector plates 201, 201a, 282, 2tl2a, and 203, 2030. Here, a resolver 205 is interfor movement as a unit, 120 apart. This makes it pos-.

sibleito initiate the sweep cycle at any point of the engine cycle. :4

'( c) Obtaining a Circular Sweep Directly From a Single- Phase Generator. (FIG. 19)

from a single phase generator 210. By utilizing parallel resistance 211 and capacitance 2112 from the generator 210, and impressing them across the respective'pairs of deflector plates'213, 214 and 215, 216 of a cathode-ray tube 217, at a. desired frequency, the impedances may be quat'e radius relative toa limited speedrange is used, this makes no difference whatever, since the optical wedge if uniform in light transmission along any given radius, will 19sh'ows how to obtain a circular sweep directly 13 compensate for it, but for other uses, it is not as suitable as some of the forms shown heretofore.

(d) Obtaining a Circular Sweep From a Three-Phase Generator Using Impedance Lag. (FIG.

The same principle used with the single-phase generator 210 can be used with the more common three-phase generators, as shown in FIG. 20. Here a generator 220 supplies current to a resolver 221 with only two brushes 222, 223 which are rotatable together 180 apart. From then on, the circuit is like that shown in FIG. 19, and the same numbers are used. This circuit makes it possible to use a single amplifier, when amplification is required, to amplify the signal before applying it to the circle-sweep cathode-ray tube.

(2) Obtaining a Circular Sweep From a Three-Phase Generator Using MagneticDefleczion Coils (FIG.

While the use of electrical deflection plates has been shown, magnetic deflection can also be used, and FIG. 25 illustrates how a three-phase generator 323 can be connected directly to a magnetic deflection yoke 316. The yoke 316 includes six coils spaced at 60 intervals, three diametrically opposite pairs, each pair being across two of the three lines 320, 321, and 322 coming from the generator 323. It sufiices to say here that the deflection again results in a circular pattern.

To those skilled in the art to which this invention relates, many changes in construction and widely diifering embodiments and applications of the invention will suggest themselves without departing from the spirit and scope of the invention. The disclosures and the description herein are purely illustrative and are not intended to be in any sense limiting.

I claim:

1. In an engine analyzer,- a first cathode-ray tube, engine-operated means to generate in said tube a circular cathode-ray sweep in cycle with the engine that generates it; means for transforming the electron beam in said circular sweep into a light beam moving in a circle; means to change the intensity of the light during each cycle according to the angular position of the light beam in its circular path; means, responsive to said change in light intensity, to correspondingly vary an electrical signal; and means to impress said electrical signal upon the sweep plates of an engine analyzer cathode-ray tube.

2. The analyzer of claim 1 in which the engine that generates the circular sweep is used as the source of a signal impressed on the other plates of the engine analyzer tube.

3. In an engine analyzer, a first cathode-ray tube, means driven by the engine being analyzed to generate in said tube a circular cathode-ray sweep in cycle with said engine; means for transforming said circular sweep into a light beam moving in a circle; means to change the intensity of the light according to its angular position during each cycle; means, responsive to said change in light intensity, to correspondingly vary an electrical signal; means to impress said electrical signal upon the sweep plates 'of an engine analyzer cathode-ray tube to 7 provide a rectilinear sweep in synchronism with the engine; and means to place a'signal to be analyzed across the other plates of said engine analyzer tube.

4. An automatically synchronized cathode-ray sweep apparatus for an engine analyzer where one set of plates of a primary cathode-ray tube is utilized for the sweep circuit and the other set of plates is made responsive to an engine initiated signal whereby the engine performance may be studied, comprising: a generator. operated by the engine being studied and therefore in synchronization with said engine, means for obtaining from said generator a plurality of substantially equal signals out of phase; an auxiliary cathode-ray tube having a corresponding plurality of pairs of deflection plates connected to said generator signals so as to generate a circular path for an electron beam in said tube; an instantaneously fluo- 14 a 4 rescent screen converting said beam into light; an optical wedge through which the light form said tube passes;fa photo-transducer receiving the light that passes through said wedge and actuated thereby to vary an electric signal; and means to impress said electric signal across said primary cathode-day tube sweep circuit plates.

5. The apparatus of claim 4 wherein said light wedge has its transmission change uniformly with change in angle thereof over its full 360 extent.

6. The apparatus of claim 4 wherein the light transmission of said light wedge changes uniformly with changes in angle over a portion of a circle and remains uniform over the remainder of said circle.

7. The apparatus of claim'4 wherein the light transmission of said light Wedge varies uniformly with changes in angle over one portion of a circle and varies uniformly with changes in angle at a different rate, over another portion of said circle.

8. The apparatus of claim 4 wherein the light transmission of said light wedge remains constant at one level over one portion of. a circle and remains constant at a difierent level over another portion of a circle.

9. The apparatus of claim 4 wherein said light wedge consists of a circular wedge with two types of segments that alternate, each of one type of segment having uniform light transmission but at a different level from that of a preceding segment of its type, each of the other type of segment changing its transmission at a uniform rate between the levels of its two adjacent segments of the other type.

10. The apparatus of claim 4 wherein said generator is a three-phase generator and wherein there are three pairs of parallel plates in axial succession in said auxiliary cathode-ray tube, the pairs lying apart, one plate of each pair being connected to one of the three poles in said generator.

11. The apparatus of claim 4 wherein said generator is a three-phase generator and wherein there are three pairs of magnetic coils spaced around said auxiliary cathode-ray tube, the two coils in each pair lying 180 apart and the pairs 60 apart and connected to the three poles in said generator.

12. The apparatus of claim 4 wherein there are two pairs of parallel deflection plates in said auxiliary cathode-ray tube, and means for obtaining from said generator two signals 90 out of phase.

13. The apparatus of claim 12 wherein'the generator is coupled to the auxiliary cathode-ray tube by a resistance coupling to one set of deflection plates and at capacitance coupling to the other set.

14. The apparatus of claim 4 wherein a plurality of said Wedges are mounted at the same radius in a rotatable disc, so that the wedges can be changed by rotating said disc.

15. The apparatus of claim 4 wherein "a lens is employed to focus the light beam on said photo-transducer.

16. An automatically synchronized eathode-ray sweep apparatus for an engine analyzer where one set of plates of a primary cathode-ray tube is utilized for the sweep circuit and the other set of plates is made responsive to an engine initiated signal whereby the engine performance may be studied, comprising: a generator operated by the engine being studied and therefore in synchronization with said engine, means for obtaining from said genera-tor two substantially equal signals 90 out of phase; an auxiliary cathode-ray tube having two pairs of parallel deflection plates connected to said generator signals so as to generate a circular path for an electron the light from said tube passes; a photo-transducer receiving the light that passes through said wedge and actuated'fthereby tovar'y anelectric signal; and means to impress said electric signal across said primary cathoderay tube sweep circuit plates.

17. An automatically synchronized cathode-ray sweep apparatus for an engine-analyzer where one set of plates of aprimary cathode-ray tube is utilized for the sweep circuit and the other set of plates is made responsive to an engine initiated signal whereby the engine performance may be studied, comprising: a generator operated by the engine being studied and therefore in synchronization with said engine, means for obtaining from said generator a plurality of substantially equal signals out of phase; an auxiliary cathode-ray tube having a corresponding-plurality of pairs of deflection plates connected to said generator signals so as to generate a circular path for an electron beam in said tube; an instantaneously fluorescent screen convertingsaid beam into light; an optical wedge through which the light from said tube passes, said wedge having a plurality of annular ccncen-o apparatus for an engine analyzer where one set of plates of a primary cathode-ray tube is utilized for the sweep circuit and the other set of plates is made responsive to an engine initiated signal whereby the engine performance may be studied, comprising: a generator operated by the engine being studied and therefore in synchronization with said engine, means for obtaining from said generator a plurality of substantially equal signals out of phase; an auxiliary cathode-ray tube having a corresponding plurality of pairs of deflection plates connected to said generator signals so as to generatea circular path for an electron beam insaid tube; an instantaneously fluorescent screen converting said beam into light; an optical wedge through which the light from said tube passes; means for rotating said wedge for changing the initiation point of the cycle; a photo-transducer receiving the light that passes through said wedge and actuated thereby to vary an electric signal; and means to impress said electric signal across said primary cathode-ray tube sweep circuit plates.

References Cited in the file of this patent UNITED STATES PATENTS 2,067,262 Demontvignier-et al. Ian. 12, 1937 2,374,666 Cunifi May 1, 1945 2,557,691 Rieber June 19, 1951 2,622,441 Richardson et al. Dec. 23, 1952 FOREIGN PATENTS 156,352 Australia Dec. 11,, 1952 

